Grease composition and process for its preparation



. proved grease compositions.

United States Patent 3,tl95,376 GREASE COMPOSETEON AND PROCESS FOR ITSPREPARA'HON Harvey E. Hook, Danville, and Harold A. Woods,

Martinez, Calii., assignors to Shell Gil Company, a corporation ofDeiaware No Drawing. Filed Nov. 16, 1959, Ser. No. 852,979 a 6 Ciaims.(ill. 252-28) This invention relates to improved lubricating greasecompositions. More particularly, the invention relates to greases gelledwith oleophilic clays and containing a combination of extreme pressureadditives as well as a process for the preparation of said grease.

Plastic lubricating compositions suit-able for general use throughoutthe mechanical arts should possess good lubricating properties and, forheavy duty use, should also inherently possess extreme pressurecharacteristics when operated in either a dry or wet environment. Thelatter condition is particularly prevalent in such industrial uses assteel rolling mill applications and the like.

It has been possible in the past to formulate clay grease compositionshaving good resistance to leaching by water as well as having desirablemechanical characteristics. The ability to operate under extremeloading, however, has not been satisfactorily obtained by the use ofmost Well known extreme pressure agents such as are employed in oil andgrease compositions. The addition of certain inorganic oil-insolublematerials to grease-s for this purpose has been suggested, but it hasbeen found in practice that if they impart any load bearing capacity tothe grease this is at a maximum only when the latter is employed insubstantially anhydrous environments. Once water is incorporated in thegrease, either purposely or accidently, the

. those originally added. This causes the formation of a film (platingout) of the oil-insoluble additive on machinery being lubricated withthe composition. Agglomeration of the particles on the other hand causesclogging of screens, plugging of lines and valves of centralizeddispensing systems, and the impartingof a grittiness to the compositionwhich is a disadvantageous feature.

It is an object of the present invention to provide im- It is aparticular object of the invention to provide a process for thepreparation of such compositions. It is a further particular object toprovide improved clay grease compositions having extreme pressureproperties not only under anhydrous conditions but under wet operatingconditions as well. Other objects will become apparent from thefollowing detailed description of the invention. t

Now, in accordance with the present invention, greases gelled witholeophilic clays can be improved with respect to their extreme pressureproperties even under wet conditions as Well as dry by the combinationtherein of an alkali metal borate and a phosphorus and sulfur reactionprod uct ofan olefinic hydrocarbon, especially a terpene, and aphosphorus sulfide. Still in accordance with this inventiona process isprovided for the preparation of such compositions which comprisesseparately forming a substantially anhydrous oleophilic clay greaseoomposition and a substantially anhydrous oil suspension of the alkalimetal bora-te in particulate form and commingling the bor-ate-oilsuspension and the grease compositiomthe phosphorus sulfide-olefinreaction product preferably being added after incorporation of thealkali metal borate. Still in accordance with a preferred aspect of theinvention,

more substantial improvements in extreme pressure properties areencountered when the subject grease compositions contain additiveamounts of one or more lead soaps (particularly a lead napthenate), withor without a chlorinated aryl disulfide and/or a chlorinatedhydrocarbon, all as more particularly described hereinafter.

Examples of the alkali metal bor-ate which may be used in thecompositions of this invention include particularly the sodium borates(both hydrated and anhydrous) and including sodium meta-borate andsodium tetraborates, of which the preferred species is borax. Potassiumbo-r-ate may be utilized, such as potassium meta-borate and potassiumtetraborate. The corresponding lithium or cesium salts may be employedin addition to or in place of the potassium or sodium salts. These areto be utilized in the form of finely divided particles, the more finelydivided the better but no critically limited particle size has beenestablished. The borates should be employed in amounts between about 2and about 10% by weight, based on the total grease composition,preferably between about 2.5 and 4.5 by weight thereof.

In accordance with the preferred process for the preparation of suchgreases, finely divided borax is suspended in the water-insolublelubricating oil prior to incorporation in the substantially anhydrousgrease composition. This is a relatively simple operation, but care mustbe exercised to Wet as effectively as possible the surfaces of thefinely divided borate with the lubricating oil. This can be accomplishedby slowly adding the oil to the borax with vigorous stirring. It ispreferred that the suspension contain 0.252.5 parts of the ho-rate foreach part by weight of the lubricating oil in which it is suspended.While the suspending operation may be conducted at about roomtemperature it may be desirable to warm the oil to a temperature betweenroom temperature and about F. for the purpose of lowering the viscosityof the oil, thereby facilitating mixing of the powdered borate and theoil if this is necessary.

The substantially anhydrous. grease composition with which the oilsuspension of the alkali metal borate is cornmingled may be well knownin the art wherein the principal gelling agent present is an olephilicclay, preferably an oleophilic montmorillinitic clay, such as b-entoniteor hectorite. The oleophilic character of the clay grease gelling agentis imparted thereto by reacting with or adsorbing on the clay surface acationic oleophilic surface aotive agent, particularly relativelyhighmolecular weight amines, amino amides, or quaternary ammoniumcompounds, all of which are known in the art.

The clays which are useful as startingmaterials for making the modifiedoleophilic clay in accordance with these known principles are thoseexhibiting substantially base exchange properties, and particularlythose exhibiting com arativel high base exchan e ro erties and conasthose referred to in US. Patent 2,531,427, issued to E. A. Hauser.Suitable cationic materials for adsorption on clays are described innumerous patents including U.S. 2,831,809 and 2,875,152. The clays arenormally converted to a satisfactory oleophilic form by the use of 0.25-

1.5 parts by weight of the cationic material for each part by weight ofthe degangued clay.

The oil ingredient in the greases provided by this invention may be anyof the oils of lubricating grade customarily used in compoundinggreases. The oil may be a refined, unrefined or semi-refined,parafiinic, naphthenic or asphaltic base mineral oil having a viscosityof from about 50 to about 4000 SUS at 100 F. Synthetic lubricants may beemployed in place of, or in addition to the mineral oils. The variousclasses of synthetic lubricants are Well known in the art and do notrequire detailed description here. Typical classes of such lubricantsinclude phosphates, such as tris(2-ethylhexyl)phosphate, dicarboxylates,such as bis(2-ethylhexyl)sebacate and corresponding silicates andborates.

The incorporation of an alkali metal borate in the described class ofoleophilic clay greases imparts a surprising amount of load carryingability and, even more unexpected, oxidation resistance, to thecompositions when they are operated in the virtual absence of water.However, it has been found that when water is present, such as mayoccur, for example, in wheel bearings under wet driving conditions or insteel mill rolling lubricants, the lubricating characteristics of thegrease are maintained but the extreme pressure properties are seriouslydegraded. Hence, the prime objective of this invention is to overcomethis disadvantageous reduction in extreme pressure properties byborate-containing greases in the presence of water. It has beendiscovered that this feature is overcome by the presence in the grease,together with the borate, of a phosphorusand sulfur-containing reactionproduct formed between an olefin hydrocarbon of at least 8 carbon atoms,and particularly a cyclic olefin such as a terpene, and a phosphorussulfide.

The agent cooperating with the borax for the preservation of extremepressure properties under wet operating conditions is preferablyprepared by reaction at temperatures between about 100 and about 160 ofa phosphorus sulfide and a bicyclic terpene or a material predominantlycomprised of a bicyclic terpene. All of the phosphorus sulfides, such asP 8 P 8 P P 8 P 8 etc. are contemplated as reactants in the preparationof these reaction products but P 8 is particularly preferred. As usedherein, the designation bicyclic terpene refers to those terpenes whichare characterized by the presence of one double bond in the molecule andbuilt up of a two-rings system. Illustrative of such compounds arepinene, camphene and fenchene. Typical oils containing such materialsare turpentine oil, the major constituent of which is pinene. i

Although a complete understanding of the chemical composition of thereaction products of phosphorus sulfides and bicyclic terpenes has notbeen achieved at this time, a partial understanding of their compositionmay be obtained by noting the characteristics involved in the reaction.For example, the reaction is exothermic and the viscosity increasesappreciably during reaction. Little, if any hydrogen sulfide is evolved.Therefore, the reaction product contains phosphorus and sulfur insubstantially the same amounts and ratios as in the particularphosphorus sulfide reacted with the terpene. It would, therefore, appearthat the reaction is one of addition, that is, addition of phosphorussulfide at a site of unsaturation present in the terpene.

(The proportions of reagents used in the preparation of these reactionproducts may be varied in order to obtain reaction products havingdifferent degrees of oil-solubility, tailored to meet the solubilitycharacteristics of the oil or grease employed. In this regard, it ispreferred that about one mole of phosphorus sulfide be reacted with fourmoles of a bicyclic terpene in order to obtain a reaction productrelatively soluble in ordinary petroleum oils. Suitable ratios for mostpurposes contemplated are 1 mole of phosphorus sulfide for 3-5 moles ofbicyclic I terpene.

The olefin-phosphorus sulfide reaction product is preferably employed inamounts between about 0.5% and about 5% by weight based on the totalgrease composition. The additive is preferably incorporated in thegreases subsequent to addition of borax. Conveniently, however, it isadded to the composition subsequent to dehydration and prior to millingof the composition for the purpose of creating a suitable greasestructure.

The addition of these reaction products has been found to have thesurprising effect of maintaining the extreme pressure properties of theborax even when water is present. The low cost of borax makes it adesirable additive to employ in large scale use, such as in steel millrolling greases. Now, with the ability to maintain the extreme pressureproperties of the borax grease even in the presence of water byincorporation of the phosphorus sulfideterpene reaction product, ahighly satisfactory low cost industrial lubricant is provided. The meansby which this maintenance of extreme pressure properties in the presenceof water is attained has not been elucidated at this time. However, ithas been determined that many other proprietary products useful inthemselves as extreme pressure agents have failed to provideborax-containing oleophilic clay greases with the desired maintenance ofextreme pressure properties in the presence of water.

The combination of alkali metal borate with the phosphorusandsulfur-containing reaction products with a bicyclic terpene cures thewater sensitivity of borax when contained in grease but does not providethe grease composition with maximum extreme pressure properties. Theseare substantially improved by the further incorporation of a leadnaphthenate to the extent of 0.25-2% based on the total weight of thegrease. The improvement in extreme pressure properties without damage tothe grease structure is a surprising feature of the invention in view ofthe mild extreme pressure properties which lead naphthenate exhibits inthe absence of other materials. Moreover, when utilized alone in amountsin excess of 1%, lead naphthenate hardened the unworked penetration of agrease so that an unduly wide spread occurred between unworked andworked penetrations. Lead naphthenates are materials well known in theart and may be prepared by reaction of lead compounds with naphthenicacids such as those obtained from certain American crudes, especiallythose obtained from California. These acids are obtained as mixtures andhave average molecular weights of about 250 or higher. In producing leadnaphthenate the requisite amount of a lead oxide, such as litharge, isadded to the acid and the temperature is raised to eifect reaction. Theproportion of lead is in the order of 25-35% and it is preferred to makethe lead naphthenate from the oxide instead of utilizing other leadsalts although these, such as carbonates, may be employed, if desired.

Still further improvements in the extreme pressure properties of thedescribed class of greases is effected by the addition of a chlorinateddiaryl disulfide. This may contain about 10% chlorine, although bothlarger and smaller percentages may be used. Bis(parach1orobenzyl)disulfide is the preferred species but other corresponding compounds maybe utilized such as bis(paraphenyl)disulfide,bis(metachloroparatolyl)disulfide and the corresponding chlorinatedxylene disulfides, as well as mixed disulfides such as paria-chlorobenzyl and para-chloro phenyl disulfide. These materials are preferablyemployed in amounts between about 0.25 and 2.5% by weight of the totalgrease composition.

Chlorinated waxes, higher molecular weight hydrocarbons, such asparatfins, may be employed in place of or in addition to the chlorinateddiaryl disulfide. The chlorinated waxes are preferably chlorinatedparafiin Wax containing from 20 to 50% chlorine, preferably from 30 to45% by Weight. Corresponding chlorinated rubber may be used.

The following examples illustrate the advantages gained by the use ofthe process and product of this invention.

Example 1 Formula. percent w. Sample A Sample B Hectorite clay 4. 905.03 Amide of 'lctraethylenepentamine and tall oil acids 3. 69 3.79Phosphoric Acid 0. 40 0. 41 Sodium Nitrite 0. 46 0. 47Ihenyl-alpha-na-phthylamine 0. 46 0. 47 Borax (Impalpable Powder) r. 3.3.00 Pass-turpentine Reaction Product. 2.00 Lead Naphthenate 0.50Lubricating Oil 84. 59 86.83

13.1. Timken Test, lbs:

0 K load, dry 50 20 OK load, wet 35 10 or less a Added to the grease asa 50/50 concentrate of borax and oil after dehydration.

b Saturated with water.

Example II vBy adding the borax as an oil-borax mixture a subrnicronsize dispersion Was obtained, no plating out Was experienced duringhomogenizing or in bearing tests, and the grease was excellent in allrespects, as long as the borax comprised at least 65% by weight ofparticles having less than 50 micron diameters. If the proportion oflarger particles is greater than about 35%, it is p neferred that theoil suspension of the borate be added to the grease at an elevatedtemperature and the resulting mixture stirred for 1560 minutes at200-300 F. in order to obtain maximum dispersion.

We claim as our invention:

1. A grease composition comprising a major proportion of a lubricatingoil, a grease-forming proportion of a colloidally dispersed clay, saidclay being Waterproofed with a cationic hydrophobic surface activeagent, 210% by weight of an alkali metal borate, at least 65% by weightof said borate being particles having diameters of less than 50 microns,O.252% by weight of a lead naphthenate and 0.55% by Weight of aphosphorusand sulfur-containing reaction product obtained b reaction ofa bicyclic terpene and a phosphorus sulfide.

2. A grease composition comprising a major proportion of a minerallubricating oil, a grease-forming proportion of a colloidally dispersedclay, said clay being Waterproofed with a cationic hydrophobic surfaceactive agent, 210% by weight of borax, 0.252% by weight of a leadnaphth-enate and 0.5-5% by Weight of a phosphorusand sulfur-containingreaction product obtained by reaction of a bicyclic terpene and aphosphorus sultide, at least 65 by weight of borax having particle sizediameters of less than 50 microns.

3. The process for the preparation of a grease containing borax whichcomprises mim'ng horax and oil together,

whereby a 'borax-oil suspension is formed and dispersing the suspensionin a substantially anhydrous oleophilic clay grease composition bymixing followed by milling, said composition containing 0.252% by Weightof a lead naphthenate and 0.55% by Weight of a phosphorusandsulfur-containing reaction product of a bicyclic terpene and aphosphorus sulfide, at least by weight of borax having particle sizediameters of less than 50 microns.

4. The process for the preparation of a grease containing an alkalimetal borate which comprises forming a suspension of 0.252.5 parts byWeight of particulate borate in 1 part of a lubricating oil, at least65% by weight of said borate being particles having diameters of lessthan 50 microns and thereafter adding the suspension to a substantiallyanhydrous oleophilic clay grease composition, said grease compositioncontaining 0.25-2% by weight of a lead napthenate and (LS-5% by weightof a phosphorus and sulfur-containing reaction product of a bicyclicterpene and a phosphorus sulfide.

5. In a process for the formation of a grease composition havingimproved extreme pressure properties in the presence of water, the stepscomprising forming a substantially anhydrous composition ofgrease-forming components, said composition comprising a majorproportion of a mineral lubricating oil, a grease-forming proportion ofan organophilic montmorillonite clay 0.252% by weight of a leadnapthenate and 0.55% by weight of a phosphorusand sulfur-containingreaction product of a bicyclic terpene and a phosphorus sulfide;separately forming a substantially anhydrous lubricating oil suspensionof 025-25 parts particulate alkali metal borate per part by Weight ofoil, :at least 65 by Weight of said borate being particles havingdiameters of less than 50 microns; and commingling the composition andsuspension.

6. In a process for the formation of a grease composition havingimproved extreme pressure properties in the presence of Water, the stepscomprising forming a substantially anhydrous composition ofgrease-forming components, said composition comprising a majorproportion of a lubricating oil, 0.'25-2% by Weight of a leadnaphthenate, a grease-forming proportion of an organophilicmontmorillonite clay and 0.5-5% by Weight of a phosphorusandsulfur-containing reaction product of a bicyclic terpene and aphosphorus sulfide; separately forming a substantially anhydrouslubricating oil suspension of 0.25-2.5 parts particulate alkali metalborate per part by weight of oil, at least 65 by weight of said boratebeing particles having diameters of less than 50 microns; and:commingling the composition and suspension.

References Cited in the file of this patent UNITED STATES PATENTS2,654,712 Cyphers et a1. Oct. 6, 1953 2,932,615 Jordan et a1. Apr. 12,1960 FOREIGN PATENTS 789,421 Great Britain Jan. 22, 1958

1. A GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF LUBRICATINGOIL, A GREASE-FORMING PROPORTION OF A COLLODIALLY DISPERSED CLAY, SAIDCLAY BEING WATERPROOFED WITH A CATIONIC HYDROPHOBIC SURFACE ACTIVEAGENT, 2-10% BY WEIGHT OF AN ALKALI METAL BORATE, AT LEAST 65% BY WEIGHTOF SAID BORATE BEING PARTICLES HAVING DIAMETERS OF LESS THAN 50 MICRONS,0.25-2% BY WEIGHT OF A LEAD NAPHTHENATE AND 0.5-5% BY WEIGHT OF APHOSPHORUS- AND SULFUR-CONTAINING REACTION PRODUCT OBTAINED BY REACTIONOF A BICYCLIC TERPENE AND A PHOSPHORUS SULFIDE.